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Probiotics, Poor Diet May Interfere with Cancer Immunotherapy

Probiotic supplements and certain foods could affect how well people respond to cancer immunotherapy, due to the way they influence the gut bacteria, suggests a new study.

This type of cancer treatment uses the body’s own immune system to prevent, target, and eliminate cancer. While this treatment is still relatively new, immunotherapy drugs have been approved to treat several types of cancer.

The new study included people with metastatic melanoma, a later-stage type of skin cancer.

Patients underwent immunotherapy with anti-PD-1 checkpoint inhibitors.

This treatment turns off the “brakes” that cancer cells use to keep T cells — part of the immune system — from killing them.

Probiotics worsen response to immunotherapy

Researchers found that patients using probiotic supplements were 70 percent less likely to respond to this type of immunotherapy.

Probiotic supplements contain live bacteria that “seed” your gut with those microorganisms.

They’re classified by the Food and Drug Administration as food supplements, so they don’t undergo rigorous testing.

People taking probiotics also had a lower diversity in their gut microbiome, the trillions of bacteria and other microorganisms that inhabit your intestines.

Study author Christine Spencer, PhD, a research scientist at the Parker Institute for Cancer Immunotherapy in San Francisco, said that in their previous study in Science, they found “a strong link between having a lot of bacterial diversity in your gut and response to cancer immunotherapy,” specifically to anti-PD-1 checkpoint inhibitors.

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